Topic 5.2 Photosynthesis

Question 1

State the word equation for photosynthesis

Answer 1

carbon dioxide + water —> glucose + oxygen

Question 2

State the symbol equation for photosynthesis

Answer 2

6CO2+ 6H2O —> C6H12O6 + 6O2

Question 3

What is meant by autotrophic?

Answer 3

organisms make complex organic compounds from simple compounds in their environment

Question 4

Define photosynthesis

Answer 4

the process by which living organisms, particularly plants and algae, capture the energy from the sun using chlorophyll and use it to convert carbon dioxide and water into simple sugars

Question 5

What are heterotrophic organisms?

Answer 5

organisms that obtain complex organic molecules by feeding on other living organisms or their dead remains

Question 6

What is the envelope of a chloroplast?

Answer 6

the outer and inner membranes along with the intermembrane space

Question 7

What are grana?

Answer 7

stacks of thylakoid membranes within a chloropast

Question 8

What is a thylakoid?

Answer 8

a membrane disc found in a grana of a chloroplast

Question 9

What are lamellae?

Answer 9

extensions of the thylakoid membranes which connect 2 or more grana, acting as a support skeleton in the chloroplast, maintaining a working distance between the grana so that they get maximum light and function as efficiently as possible

Question 10

What is the stroma?

Answer 10

the matrix which surround the grana and contains all the enzymes needed to complete the process of photosynthesis and produce glucose

Question 11

What is chlorophyll a?

Answer 11

a blue-green photosynthetic pigment, found in all green plants

Question 12

What is chlorophyll b?

Answer 12

a yellow-green photosynthetic pigment

Question 13

What are carotenoids?

Answer 13

photosynthetic pigments made up of orange carotene and yellow xanthophyll

Question 14

What is phaeophytin?

Answer 14

a grey pigment which is a breakdown product of the other photosynthetic pigments

Question 15

Define photosystem I

Answer 15

a combination of chlorophyll pigments which absorbs light of 700nm wavelength and involved in cyclic and non-cyclic phosphorylation

Question 16

Define photosystem II

Answer 16

a combination of chlorophyll pigments which absorbs light of 680nm and only involved in non-cyclic phosphorylation

Question 17

Where are PSIs found?

Answer 17

intergranal lamellae (join the granum together)

Question 18

Where are PSIIs found?

Answer 18

on the grana

Question 19

Define absorption spectrum

Answer 19

the range of different wavelengths of light that a photosynthetic pigment absorbs against the wavelength of light (displayed as a graph)

Question 20

Define action spectrum

Answer 20

the rate of photosynthesis against the wavelength of light absorbed, displayed as a graph

Question 21

What are the 2 stages of photosynthesis?

Answer 21

• light-dependent

- light-independent

Question 22

What does the light-dependent consist of?

Answer 22

photolysis and phosphorylation to generate ATP and split water molecules

Question 23

What are the 2 types of phosphorylation?

Answer 23

cyclic and non-cyclic

Question 24

What does the light-independent stage consist of?

Answer 24

the Calvin cycle

Question 25

Which photosystem is used in cyclic phosphorylation?

Answer 25

photosystem I

Question 26

Which photosystem is used in non-cyclic phosphorylation?

Answer 26

photosystem I and II

Question 27

Describe the process of the light-dependent stage

Answer 27

1) electrons become excited and move up an energy level using the energy trapped in the thylakoid membrane
2) The electrons move along the ETC through electron carriers which generates ATP via phosphorylation of ADP
3) In non-cyclic phosphorylation reduced NADP is generated as the electrons and a proton are are transferred to NADP
- both ATP and reduced NADP are used in the light-independent stage

Question 28

Describe the process of cyclic phosphorylation

Answer 28

1) Photon of light hits chlorophyll molecule in PSI
2) Electron is excited and leaves molecule
3) Electron taken up by an electron acceptor and passed along an ETC to produce ATP
4) Electron returns to chlorophyll molecule in PSI which can be excited again

Question 29

Describe the process of non-cyclic phosphorylation

Answer 29

1) water molecules split to provide hydrogen ions to reduced NADP
2) photon of light hits chlorophyll and excites them so they are picked up by electron carriers
3) an excited electron from PSII is picked up by electron carriers and passed along ETC to PSI

Question 30

Describe how carbon fixation takes place in the chloroplasts

Answer 30

• carbon dioxide diffuses into the stroma
• carbon dioxide binds to RuBP using RUBISCO
• resulting in the formation of intermediate 6C compound

Question 31

State what happens in the Calvin cycle

Answer 31

1) carbon dioxide diffuses into the stroma and bind to RuBP using RUBISCO
2) intermediate 6C compound forms which immediately splits to 2 x GP (3C)
3) GP is reduced by reduced NADP (goes from reduced NADP –> NADP) and ATP from light-dependent stage is used (ATP –> ADP)
4) this forms GALP ( 2 x 3C)
5) GALP loses a C which forms glucose after 6 turns of the Calvin cycle and ATP is used

Question 32

State the difference between an action spectrum and an absorption spectrum

Answer 32

absorption spectrum shows absorption of light of different wavelengths and action spectrum shows rate of photosynthesis at each wavelength